AW: question about index cost estimates

From: Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at>
To: "'Tom Lane'" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "'pgsql-hackers(at)postgresql(dot)org'" <pgsql-hackers(at)postgresql(dot)org>
Subject: AW: question about index cost estimates
Date: 2000-05-18 07:29:31
Message-ID: 219F68D65015D011A8E000006F8590C604AF7D8B@sdexcsrv1.f000.d0188.sd.spardat.at
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> It seemed to me that the critical ratios are #tuples fetched vs #pages
> in table and table size vs. cache size. I could be wrong though...

Another metric that would be interesing is a number that represents
the divergence of the heap order from the index sort order.

If heap data is more or less in the same order as the index
(e.g. cluster index) the table size is irrelevant.
So the measure would be something like
clustered*tablesize vs cache size instead of only tablesize.

Andreas

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